Causal information velocity in fast and slow pulse propagation in an optical ring resonator

Abstract

We examined the propagation of nonanalytical points encoded on temporally Gaussian-shaped optical pulses in fast and slow light in an optical ring resonator at λ = 1.5 μm. The temporal peak of the Gaussian pulse was either advanced or delayed, reflecting anomalous or normal dispersions in the ring resonator, relevant to under-or overcoupling conditions, respectively. The nonanalytical points were neither advanced nor delayed but appeared as they entered the ring resonator. The nonanalytical points could be interpreted as information; therefore, the experimental results suggested that information velocity is equal to the light velocity in vacuum or the background medium, independent of the group velocity. The transient behaviors at the leading and trailing edges of the nonanalytical points are discussed in terms of optical precursors.

Direct Observation of a Pulse Peak Using a Peak-Removed Gaussian Optical Pulse in a Superluminal Medium

“…The discontinuous point was neither advanced nor delayed, but appeared in the output instantly as it entered the system. A sharp nonanalytical point with an infinite frequency range cannot move faster than c, as this is the maximum limit of the traveling speed of the pulse front [19][20][21][22][23]. In our experiments, the fall time of the discontinuous point was 2.0 ns, i.e., 500 MHz.…”

Optical precursors with competing linear and nonlinear dispersions in quantum dot molecules

“…Also, the precursor behaviors have been reported in ZnTe crystal [15] and optically pumped crystals [16]. Nowadays, new experiments push optical precursors to applications further, such as the speed of precursors was measured using polarizationbased interference [17], and the causal information velocity involving precursors was examined by encoding nonanalytical points on Gaussian pulses in an optical ring resonator [18]. But the above works are studied in linear regime and few works cover nonlinear effects on propagation dynamics of optical precursors in solid materials.…”

Coherent control of optical precursors in a warm atomic system with Doppler effects

“…Simulation results show that the precursor intensity is inverse to the system temperature and also determined by the input-pulse form. Optical precursors could be much enhanced by Doppler effects [24], and here more attention is paid to the effects of the control field, system temperature and pulse forms. We also notice many quantum optical phenomena have been carried out via ARG process, such as subluminal [25] and superluminal propagation [26], Kerr effect [27], optical solitons [28], gain spectrum [29], and so on.…”